A098897 Palindromic deficient numbers.

1, 2, 3, 4, 5, 7, 8, 9, 11, 22, 33, 44, 55, 77, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 232, 242, 262, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 424, 434, 454, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Example

a(10)=22 because 22 is the tenth deficient number which is palindromic also.

Mathematica

Select[Range@ 900, And[DivisorSigma[1, #] < 2 #, PalindromeQ@ #] &] (* Michael De Vlieger, Nov 08 2017 *)
nxtPal[n_]:=With[{c=Join[{2}, Flatten[Table[{10 10^d, 11 10^d}, {d, 0, 10}]]]}, SelectFirst[n+c, PalindromeQ]]; Join[{1, 2, 3, 4, 5, 7, 8}, Select[ NestList[ nxtPal[#]&, 9, 100], DivisorSigma[1, #]<2#&]] (* Harvey P. Dale, Nov 14 2024 *)

Prog

(PARI) isok(n) = (sigma(n) < 2*n) && (d=digits(n)) && (Vecrev(d) == d); \\ Michel Marcus, Nov 08 2017

Crossrefs

Intersection of A002113 and A005100.

Sequence in context: A080664 A230762 A098776 * A265641 A192140 A084092

Adjacent sequences: A098894 A098895 A098896 * A098898 A098899 A098900

Keyword

easy,nonn,base

Author

Shyam Sunder Gupta, Oct 14 2004

Status

approved